The main objective of our research is to study protein nucleic acid interactions so that a more profound understanding of the molecular forces that govern this process can be obtained. In particular we will examine the consequences of photo induced crosslinking of E. coli RNA polymerase with SV40 DNA and DNA both in terms of the protein subunits that are involved and the regions of the DNA that are shielded from nuclease digestion. We hope that by actually determining which amino acid residues and which nucleotides are covalently linked, we will be able to get more information about the molecular details of the interaction that confers specificity on the protein-nucleic acid complex. The opportunity for getting this type of data should be most favorable with the fd gene 5 protein as well as with the fd coat protein crosslinked to fd DNA or (BrdU)-substituted fd DNA. Our studies on the genetics, regulation, crystallization and structure function relationships of aminoacyl-tRNA-synthetases and their cognate tRNAs will be continued since it offers another avenue for understanding protein- nucleic interactions. We will finish our work on the amino acid sequence and chemical modification of the C chain of aspartyl transcarbamylase from E. coli. Our proposed studies on the T4 gene-32-protein and gene 5 proteins from other filamentous DNA phages will add to our knowledge about the mode of action of these DNA binding proteins and round out our program which has the specificity of DNA-protein binding as its main theme.